Technical Field
[0001] The present invention relates to a vehicle control device for implementing sailing
stop control that sets a transmission to a neutral state under prescribed control
conditions, and also stops a drive source.
Background Art
[0002] In recent years, there has been developed a technique (sailing stop control) that,
when prescribed control conditions are established while a vehicle is traveling, is
used for both control of a transmission to a neutral state (sailing control) and control
to stop a drive source, promoting energy saving (see Patent Document 1).
[0003] The conditions (A) to (D) noted hereafter are included as AND conditions in the control
conditions of this sailing stop control.
- (A) Forward range is selected.
- (B) Vehicle speed is a set vehicle speed or greater (medium to high vehicle speed).
- (C) Accelerator is off.
- (D) Brake is off.
[0004] However, when the vehicle is equipped with a continuously variable transmission,
provision is such that before stopping the vehicle, the shift ratio of a variator
of the continuously variable transmission is downshifted to the lowest level, and
restart is done thereafter.
[0005] In such a vehicle, when there is sudden deceleration from sailing stop control and
the vehicle reaches a stop, it was found that there are cases when the vehicle cannot
downshift to the lowest level before stopping.
[0006] The causes of this are analyzed.
[0007] With sailing stop control, in a state for which the vehicle speed of the abovementioned
condition (B) is a set vehicle speed or greater (medium to high speed), the drive
source is stopped, the shift ratio of the variator in the medium to high vehicle speed
is at the high side, and the transmission has the forward clutch released and is in
neutral.
[0008] When a sudden braking operation is performed from sailing stop control, sailing stop
control is cancelled, return control is performed that operates the drive source and
engages the forward clutch, and after the forward clutch is engaged, the variator
shift ratio is downshifted to the lowest level.
[0009] Engaging the forward clutch before downshifting the variator is done because it is
possible to do rotation synchronization of the forward clutch more quickly than when
the shift ratio of the variator is on the high side.
[0010] However, when attempting to downshift the variator after engagement of the forward
clutch in this way, the vehicle stops before it is possible to downshift to the lowest
level of the target shift ratio.
[0011] The variator performs changing (shifting) of the shift ratio while rotating, so shifting
takes more time the slower the rotational speed, and in particular with transmissions
of a configuration for which the forward clutch is arranged at the downstream side
of the variator, when the vehicle is stopped in a state with the forward clutch engaged,
the variator also stops, and rotation is not possible, so it becomes completely impossible
to shift the variator.
[0012] Therefore, if the vehicle speed when a sudden braking operation is performed from
sailing stop control is high speed, it is possible to complete the shift operation
while the variator is rotating at a rotational speed that is a certain level or higher,
but if the vehicle speed is medium speed, there are cases when the vehicle stops before
the shift operation is completed.
[0013] Also, hydraulic pressure is generated by a hydraulic pump driven by the vehicle drive
source engine, and when the variator is controlled using this hydraulic pressure,
when the vehicle speed decreases and engine rotation decreases, the necessary hydraulic
pressure cannot be obtained, and shifting of the variator is difficult.
[0014] Therefore, it is necessary to complete downshifting of the variator in a state for
which the necessary hydraulic pressure can be obtained.
Prior Art Documents
Patent Documents
[0015] Patent Document 1: Japanese Unexamined Patent Publication No.
2013-213557
Summary of the Invention
[0016] The present invention was created considering this kind of problem, and its purpose
is, in a vehicle provided with a continuously variable transmission having a variator,
to provide a vehicle control device that is able to improve the low return performance
for downshifting the shift ratio of the variator to the lowest level before the vehicle
stops, even when a braking operation is performed during sailing stop control.
[0017] To achieve the abovementioned purpose, the vehicle control device of the present
invention is a control device of a vehicle which has: a drive source; and an automatic
transmission which has an engagement element for disconnecting/connecting the transmission
of the driving force and a variator placed further upstream than the engagement element,
and which is connected to the drive source, said vehicle control device having: a
first control unit that executes sailing stop control that, when sailing stop conditions
are established, stops the drive source and also puts the automatic transmission into
a neutral state; and a second control unit that, when a prescribed sailing stop cancellation
condition among the sailing stop cancellation conditions is established, and the sailing
stop control is cancelled, when the size of the deceleration level of the vehicle
is a prescribed value or greater, starts the drive source and implements downshifting
of the variator, and engages the engagement element after downshifting is complete.
[0018] When the sailing stop control is cancelled, and when the size of the vehicle deceleration
level is less than the prescribed value, the second control unit preferably starts
the drive source and engages the engagement element, and moves to control of the variator
after engaging of the engagement element.
[0019] It is preferable that the prescribed value be set to vary according to the travel
speed of the vehicle when cancelling the sailing stop control.
[0020] Included as AND conditions in the sailing stop conditions are: the selection range
of the automatic transmission being the forward range, the traveling speed of the
vehicle being a set speed or greater, the accelerator of the vehicle being off, and
the brake of the vehicle being off, with the sailing stop cancellation condition being
that any of the sailing stop conditions are no longer established, and the prescribed
sailing stop cancellation condition being that the brake is on being preferable.
[0021] Once starting of the drive source and engagement of the engagement element by the
second control unit is completed, normal control is preferably implemented in which
the engagement of the engagement element is maintained, output of the drive source
is controlled according to the accelerator opening degree of the vehicle, and the
shift ratio of the variator is controlled according to a preset shift map.
[0022] The drive source is an internal combustion engine, and having a third control unit
that implements fuel cut control that stops fuel supply to the internal combustion
engine if a fuel cutting condition is established is preferable.
[0023] With the present invention, when sailing stop control ends in a state with a high
deceleration level of the vehicle due to sudden braking, etc., the drive source restarts,
engagement of the engagement element is given priority, and shifting of the variator
is completed, so the low return performance of the variator is improved, it is possible
to have the shift ratio of the variator reach the lowest level or be as close as possible
to the lowest level by the time the vehicle stops, and possible to ensure restart
capability of the vehicle.
Brief Description of the Drawings
[0024]
FIG. 1 is a system diagram showing the main parts of the driving system and control
system of the vehicle to which the control device of an embodiment of the present
invention is applied.
FIG. 2 is a diagram showing a control map using the vehicle control of the embodiment
of the present invention.
FIG. 3 is a shift chart for explaining the shift ratio characteristics of the variator
related to the vehicle control of the embodiment of the present invention.
FIG. 4 is a flow chart for explaining the vehicle control of the embodiment of the
present invention.
FIG. 5 is a time chart for explaining the return control (variator downshift priority)
of the vehicle control of the embodiment of the present invention.
FIG. 6 is a time chart for explaining the return control (forward clutch engagement
priority and vehicle stop) of the vehicle control of the embodiment of the present
invention.
FIG. 7 is a time chart for explaining the return control (forward clutch engagement
priority and vehicle travel continuation) of the vehicle control of the embodiment
of the present invention.
Modes for Carrying Out the Invention
[0025] Hereafter, embodiments of the present invention are explained while referring to
the drawings. The embodiments shown hereafter are merely examples, and are not intended
to exclude application of various changes or technology not shown in the embodiments
below. Each configuration of the embodiments hereafter can be implemented with various
changes in a range that does not stray from the gist thereof, and it is possible to
make choices as necessary, or combine as appropriate.
1. Overall System Configuration
[0026] FIG. 1 is an overall system diagram showing the driving system and the control system
of the vehicle to which the control device of this embodiment is applied.
[0027] As shown in FIG. 1, the driving system of the vehicle is provided with: an engine
(internal combustion engine) 1 that is the drive source; a torque converter 2; a variator
(continuously variable transmission mechanism) 3; a forward/reverse switching mechanism
4 that has a forward clutch (engagement element) 41; a final deceleration mechanism
(not illustrated); a differential (not illustrated); and a drive wheel 5.
[0028] By storing the torque converter 2, the variator 3, and the forward/reverse switching
mechanism 4 inside a transmission case, a continuously variable transmission (hereafter
also called "CVT" or simply "transmission") 100 as an automatic transmission is configured.
[0029] A mechanical oil pump 10P driven by the engine 1 is connected to the engine 1, and
the oil pump 10P pressurizes the hydraulic oil [ATF (Automatic Transmission Fluid)]
according to the rotation of the engine 1, and supplies it to hydraulic equipment
of the transmission 100.
[0030] The torque converter 2 is a starting element that has a torque increasing function,
and has as structural components a pump impeller 23 connected to an engine output
shaft 11 via a converter housing 22, a turbine runner 24 connected to a torque converter
output shaft 21, and a stator 25 provided in the case with a one way clutch interposed
(not illustrated).
[0031] The torque converter 2, when the torque increasing function is not needed, has a
lock-up clutch 20 that can directly connect the engine output shaft 11 (= torque converter
input shaft) and the torque converter output shaft 21.
[0032] Though not illustrated, the lock-up clutch 20 operates in response to differential
pressure PA-PR between the torque converter apply pressure PA and the torque converter
release pressure PR at the input side and output side.
[0033] In other words, when the release pressure PR is higher than the apply pressure PA,
the lock-up clutch 20 is released, and when the release pressure PR is lower than
the apply pressure PA, the lock-up clutch 20 is engaged.
[0034] Therefore, by adjusting the release pressure PR and the apply pressure PA, between
the input/output elements of the torque converter 20 can be switched between a released
state, a completely engaged state (directly connected state), and a slipped engagement
state that is intermediate to these.
[0035] The variator 3 has a primary pulley 31, a secondary pulley 32, and a belt (or chain)
33 as a power transmitting member, and is provided with a continuously variable transmission
function that changes the winding radius to the pulleys 31, 32 of the belt 33 by hydraulic
pressure control of the hydraulic oil, and continuously changes the shift ratio (transmission
input rotation speed/transmission output rotation speed) which is the ratio of the
input rotation speed of the variator input shaft (transmission input shaft) 34 and
the output rotation speed of the variator output shaft 35.
[0036] With FIG. 1, the torque converter output shaft 21 and the variator input shaft 34
have the same axis, but there are also cases of using a configuration with which the
torque converter output shaft 21 and the variator input shaft 34 use different axes,
and power connection is done via a gear mechanism, etc.
[0037] Though details are not illustrated, the primary pulley 31 is configured by a fixed
pulley and a slide pulley, and the slide pulley does sliding movement in the axial
direction according to hydraulic pressure (primary pressure or primary pulley pressure)
led to the primary hydraulic chamber.
[0038] Similarly, the secondary pulley 32 is configured by a fixed pulley and a slide pulley,
and the slide pulley does sliding movement in the axial direction according to hydraulic
pressure (secondary pressure or secondary pulley pressure) led to the secondary hydraulic
chamber.
[0039] The sheave surfaces which are each opposing surface of each fixed pulley and slide
pulley of the primary pulley 31 and the secondary pulley 32 all form a V shape, and
the belt 33 is extended across the V shaped sheave surfaces of the primary pulley
31 and the secondary pulley 32, and power is transmitted by contact with each sheave
surface of both end parts of the belt 33.
[0040] The winding radius of the belt 33 on the primary pulley 31 and the secondary pulley
32 is changed according to the sliding movement of each slide pulley of the primary
pulley 31 and the secondary pulley 32, and the shift ratio is changed.
[0041] The forward/reverse switching mechanism 4 is a mechanism for switching between forward
and reverse using a planetary gear mechanism (not illustrated), and has a forward
clutch (the engagement element for disconnecting/connecting transmission of the driving
force of the present invention) 41 for reaching forward levels, and a reverse engagement
element (not illustrated) for reaching the reverse level, and each of these friction
engagement elements undergoes engagement and release according to the hydraulic pressure
supplied and exhausted with each hydraulic chamber.
[0042] In the case of this control device, the engagement element can be equipped downstream
of the variator 3, and instead of the forward/reverse switching mechanism 4, for example,
it is also possible to equip an auxiliary transmission mechanism which is a stepped
transmission mechanism with two forward gears and one reverse gear, for example.
[0043] In this case, the auxiliary transmission mechanism can be configured, for example,
provided with a Ravigneaux planetary gear mechanism with two planetary gear carriers
connected, and a plurality of friction engagement elements connected to a plurality
of rotation elements that configure the Ravigneaux planetary gear mechanism, and change
the linking state thereof.
[0044] In regards to this kind of transmission 100, the hydraulic pressure of the primary
hydraulic chamber and the secondary hydraulic chamber of the variator 3, the hydraulic
chamber of each friction engagement element of the forward/reverse switching mechanism
4 and each hydraulic chamber of the lock-up clutch 20 is controlled through a hydraulic
pressure control valve 10V corresponding respectively to each.
[0045] Each hydraulic pressure control valve 10V is a solenoid valve equipped inside the
hydraulic control unit 10, is operated by command signals from an ATCU 7 as a shift
control means described later, and controls pressure regulation of the hydraulic oil
supplied from the oil pump 10P and the supply and exhaust to each hydraulic chamber.
2. Control System Configuration
[0046] As control means for controlling the vehicle, this vehicle is provided with: a travel
ECU 6 as a travel control means that is an electronic control unit for controlling
traveling of the vehicle; an ATCU 7 as a shift control means which is an electronic
control unit that controls automatic transmission; and an engine ECU 8 as an engine
control means that is an electronic control unit that controls the engine 1.
[0047] The travel ECU 6, ATCU 7, and engine ECU 8 are all configured provided with an input/output
device, a storage device (ROM, RAM, etc.) with many control programs built in, a central
processing device (CPU), and a timer counter, etc.
[0048] The travel ECU 6 has a function (first control unit) 61 that executes sailing stop
control when sailing stop conditions are established, and a function (second control
unit) 62 that cancels the sailing stop control and returns to normal traveling when
a cancellation condition for this sailing stop control is established.
[0049] Furthermore, the travel ECU 6 has a function (third control unit) 63 that executes
fuel cut control for stopping fuel supply to the engine 1 when the fuel cutting condition
is established.
[0050] The return control that cancels the sailing stop control by the first control unit
61 and the sailing stop control by the second control unit 62 and returns to normal
traveling is implemented by the control of the transmission 100 through the ATCU 7
and the control of the engine 1 through the engine ECU 8.
[0051] Also, the fuel cut control by the third control unit 63 is implemented by the control
of the engine 1 through the engine ECU 8.
[0052] The ATCU 7 has: a shift ratio control unit (shift ratio control means) 71 that adjusts
the hydraulic pressure of each hydraulic chamber of the variator 3 and controls the
shift ratio; a forward/reverse switching control unit (forward/reverse switching control
means) 72 that adjusts the hydraulic pressure of each hydraulic chamber of the forward/reverse
switching mechanism 4 and switches between forward and reverse; and a lock-up clutch
control unit (lock-up clutch control means) 73 that adjusts the hydraulic pressure
of each hydraulic chamber of the lock-up clutch 20 and switches the engaged state.
[0053] The engine ECU 8 controls the fuel supply amount and supply time, the opening degree
of the throttle valve, and the ignition timing, etc., of the engine 1.
[0054] The sailing stop control does control used for both controlling the transmission
100 to a neutral state (sailing control) and controlling the engine (drive source)
1 to stop, and by doing this, promotes energy saving.
[0055] For the sailing stop conditions for performing this sailing stop control, the following
conditions (A) to (D) are provided as AND conditions.
- (A) Forward range is selected.
- (B) Vehicle speed (vehicle traveling speed) Vsp is a set vehicle speed (set speed)
Vsp1 or greater (medium to high vehicle speed).
- (C) Accelerator is off.
- (D) Brake is off.
[0056] For this reason, detection information from an inhibitor switch 91 for detecting
the selection range of the transmission 100, a vehicle speed sensor 92, an accelerator
opening degree sensor 93, and a brake sensor 94 are input to the travel ECU 6, and
with the first control unit 61, sailing stop conditions are determined based on detection
signals from these sensors.
[0057] "Forward range is selected" of condition (A) is determined from whether or not the
selection range signal S from the inhibitor switch 91 correlates to the forward range.
[0058] "Vehicle speed Vsp is a set vehicle speed Vsp1 or greater" of condition (B) is determined
from whether or not the vehicle speed signal Vsp from the vehicle speed sensor 92
is the set vehicle speed Vsp1 or greater.
[0059] "Accelerator is off" of condition (C) means the accelerator operation is not implemented,
and is determined from whether or not the accelerator opening signal APO from the
accelerator opening degree sensor 93 indicates an opening degree of 0.
[0060] "Brake is off" of condition (D) means the braking operation is not implemented,
and is determined from whether or not the detection signal from the brake sensor 94
indicates that the brake is on.
[0061] Having all of the abovementioned sensors that are involved in sailing stop control
be normal is a prerequisite, and this prerequisite and having all of the abovementioned
conditions (A) to (D) be established is a condition for performing sailing stop control.
[0062] With the first control unit 61, as the sailing stop control, the transmission 100
is put to a neutral state, and the engine 1 is stopped. At this time, the shift ratio
of the variator 3 is fixed at the highest state or close to the highest state, and
the lock-up clutch 20 is released.
[0063] With normal shift control of the variator 3, when the accelerator is off, the shift
ratio is controlled along a target shift line L shown by the solid line in FIG. 2,
so if the vehicle speed is a medium to high vehicle speed, the shift ratio is in the
highest state or close to the highest state shown by the dotted line.
[0064] The sailing stop conditions include condition (B) for which the vehicle speed is
medium to high vehicle speed, and condition (C) for which the accelerator is off,
so when sailing stop control starts, the shift ratio is in the highest state or close
to the highest state of the medium to high vehicle speed in the target shift line
L shown in FIG. 2.
[0065] During sailing stop control, while the forward clutch 41 is released on the one hand,
during return control when the sailing stop control is cancelled and there is a return
to normal control, the released forward clutch 41 is engaged, so there is a desire
to perform this engagement quickly. As a result, it is possible to make the return
to normal control earlier, and possible to improve the vehicle driving performance.
[0066] To engage the forward clutch 41, it is necessary to do rotation synchronization between
input and output before engaging the forward clutch 41, and it is possible to have
the high side of the shift ratio of the variator 3 complete rotation synchronization
more quickly, and possible to perform engaging of the forward clutch 41 quickly.
[0067] In other words, when returning from sailing stop control to normal control, the engine
1 is started and the forward clutch 41 is engaged, but the output side (drive wheel
5 side) of the forward clutch 41 rotates at a comparatively high speed correlating
to the vehicle speed Vsp, and meanwhile, the input side (variator 3 side and engine
1 side) of the forward clutch 41 starts rotating from a stopped state.
[0068] If the shift ratio of the variator 3 is at the high side, compared to the primary
shaft rotation speed Np (corresponding to engine speed Ne) of the variator 3, the
secondary shaft rotation speed Ns (corresponding to the input side rotation speed
of the forward clutch 41) of the variator 3 is a higher speed, so the input side rotation
of the forward clutch 41 goes to high speed quickly, and it is possible to shorten
the synchronization time with the output side of the forward clutch 41.
[0069] Also, the cancellation condition of the sailing stop control is that during sailing
stop control, any of the sailing stop conditions of the abovementioned conditions
(A) to (D) is no longer established.
[0070] With the second control unit 62, when any of the sailing stop conditions is no longer
established, the cancellation condition for the sailing stop control is regarded as
being established, sailing stop control is canceled, and there is a return to normal
control.
[0071] This second control unit 62, when canceling the sailing stop control, restarts the
engine 1 and engages the forward clutch 41, but when the sailing stop control is canceled
by the brake being on, shift ratio control of the variator 3 is added to these.
[0072] In other words, with the second control unit 62, when the brake is on and the sailing
stop cancellation condition is established, command signals are output to the ATCU
7 and the engine ECU 8 so that the engine 1 is started, the forward clutch 41 is engaged,
and the shift ratio of the variator 3 is downshifted to the lowest side.
[0073] With the shift ratio control unit 71 of the ATCU 7, this downshift is performed by
feedback control based on signals relating to the primary pulley rotation speed Np
and the secondary pulley rotation speed Ns detected by the primary pulley rotation
sensor 95 and the secondary pulley rotation sensor 96.
[0074] In this way, downshifting the shift ratio of the variator 3 to the lowest side is
provided for when the vehicle is restarted after the vehicle stops due to the brake
being on, and is to ensure vehicle start performance by having the shift ratio of
the variator 3 be at the lowest level or close to lowest level state.
[0075] This kind of return control ends after completion of the start of the engine 1 and
the engagement of the forward clutch 41, and thereafter goes to normal control.
[0076] When there is sailing stop cancellation due to the brake being on, in addition to
the engagement of the forward clutch 41, downshifting of the variator 3 is performed,
but with the second control unit 62, during this return control, the two processes
of the engagement of the forward clutch 41 and the downshifting of the variator 3
are implemented with priority sequence given based on the size of the deceleration
level of the vehicle (scalar quantity of the deceleration level, specifically, the
absolute value) d.
[0077] In other words, the second control unit 62 gives priority to downshifting of the
variator 3 when the size of the vehicle deceleration level (hereafter also simply
called deceleration level) d is a preset determination threshold value (prescribed
value) d
V or greater, and gives priority to engagement of the forward clutch 41 when the vehicle
deceleration level d is less than the determination threshold value d
V.
[0078] Therefore, when the sailing stop cancellation condition is established, the second
control unit 62 outputs command signals to the ATCU 7 and the ECU 8 so as to, when
the vehicle deceleration level d is the determination threshold value (prescribed
value) dv or greater, start the engine 1 and implement downshifting of the variator
3, and when downshifting of the variator 3 is completed, engage the forward clutch
41.
[0079] Also, when the sailing stop cancelation condition is established, when the vehicle
deceleration level d is less than the determination threshold value d
V, the second control unit 62 starts the engine 1, implements engagement of the forward
clutch 41, and after engagement of the forward clutch 41 is completed, downshifts
the variator 3.
[0080] In this way, when the vehicle deceleration level d is the determination threshold
value d
V or greater, downshifting of the variator 3 has priority, so even if the time until
the vehicle decelerates and stops is extremely short, the forward clutch 41 is not
engaged, and the variator 3 is not connected to the wheels, so a state for which the
variator 3 is rotated by the engine I is ensured. As a result, the low return performance
of the variator 3 is improved, it is possible to downshift the shift ratio of the
variator 3 to the lowest level or close to that, and the vehicle start performance
thereafter is ensured.
[0081] To change the shift ratio of the variator 3, it is necessary for the variator 3 to
be rotating and for the discharge pressure of the oil pump 10P to be ensured at a
minimum level or greater. Also, to ensure that the discharge pressure of the oil pump
10P is a minimum level or greater, it is necessary to sufficiently ensure that the
rotation speed of the engine 1 is the necessary rotation speed or greater.
[0082] Therefore, when the vehicle has stopped, or when the rotation speed of the engine
1 is insufficient and there is not sufficient discharge pressure of the oil pump 10P
(in this case, if hydraulic pressure is supplied to the forward clutch 4, there is
a further reduction in the supply of hydraulic pressure to the variator 3, and shifting
of the variator 3 becomes extremely difficult), it becomes impossible to change the
shift ratio of the variator 3.
[0083] In light of that, when there is no spare time until the vehicle stops and the rotation
speed of the engine 1 decreases to an insufficient state, before the vehicle stops,
and while it is possible for the rotation speed of the engine 1 to ensure the discharge
pressure of the oil pump 10P at a minimum limit or greater, downshifting of the variator
3 is implemented with priority.
[0084] However, when there is time to spare until the vehicle stops or the rotation speed
of the engine 1 decreases to an insufficient state, the engagement of the forward
clutch 41 has priority, and even if downshifting of the variator 3 starts after engagement
of the clutch 41 is completed, it is possible to complete downshifting of the variator
3 until the vehicle stops or until the rotation speed of the engine 1 decreases.
[0085] This is because, as described previously, rotation synchronization is necessary between
input and output before engaging the forward clutch 41, and it is possible for the
high side of the shift ratio of the variator 3 to complete rotation synchronization
faster. and possible for the engagement of the forward clutch 41 to be done faster.
[0086] As shown in the determination map of FIG. 3, the determination threshold value d
V is set to be variable according to the vehicle speed Vsp of the vehicle, and is set
with a tendency so that the lower the vehicle speed Vsp, the smaller the determination
threshold value d
V.
[0087] This is because the time until the vehicle stops or the time until the rotation speed
of the engine 1 decreases is related not only to the vehicle deceleration level d
at the point when the sailing stop cancellation condition is established, but also
to the vehicle speed Vsp at that point.
[0088] In other words, the time until the vehicle stops or the time until the rotation speed
of the engine 1 decreases to an insufficient state depends on the vehicle deceleration
level d and the vehicle speed Vsp at the time of deceleration start, and the larger
the deceleration level d, the shorter it is, and the lower the vehicle speed Vsp at
the time of deceleration start, the shorter it is. In light of that, this is set with
a tendency so that the lower the vehicle speed Vsp, the smaller the determination
threshold value dv.
[0089] With the determination map shown in FIG. 3, in the high speed range for which the
vehicle speed Vsp is at a prescribed vehicle speed value Vsp2 or greater, engagement
of the forward clutch 41 is set to have priority regardless of the deceleration level
d.
[0090] This is because in this kind of high speed range of the vehicle, it is sufficient
to decelerate while tracing the highest level line in the target shift line L shown
by a solid line in FIG. 2, so downshifting of the variator 3 is sufficiently completed
even after engagement of the forward clutch 41.
[0091] Also, in the medium speed range for which the vehicle speed Vsp is at the prescribed
vehicle speed value Vsp2 or less, as long as the deceleration level d is not slow
deceleration of a prescribed low deceleration level d1 or less, the downshifting of
the variator 3 is set to have priority.
[0092] This is because with this kind of medium speed range, as shown by the dotted line
in FIG. 2, a case is assumed of decelerating while tracing the highest level line
skewed from the target shift line L, and as long as the deceleration level d is not
slow deceleration of a prescribed low deceleration level d1 or less, there is a high
risk of not being able to complete downshifting of the variator 3 after engaging of
the forward clutch 41.
[0093] With normal control, while maintaining the engaged state of the forward clutch 41,
the output of the engine 1 is controlled according to the accelerator opening degree
APO, and the shift ratio of the variator 3 is controlled according to a preset shift
map.
[0094] When sailing stop control by the first control unit 61 is implemented, normal control
is implemented after going through return control (cancelation of sailing stop control)
by the second control unit 62.
[0095] As noted previously, return control ends at the stage when the engagement of the
forward clutch 41 is completed, so when downshifting of the variator 3 has priority,
there is a return to normal control when downshifting of the variator 3 is completed
and furthermore, engagement of the forward clutch 41 is completed.
[0096] Also, when engagement of the forward clutch 41 has priority, there is a return to
normal control if the engagement of the forward clutch 41 is completed, but even when
returned to normal control, if the brake on state continues, downshifting of the variator
3 is implemented.
[0097] Fuel cut control by the third control unit 63 is control for stopping the fuel supply
to the engine 1 and suppressing the fuel consumption amount, and also for strengthening
engine braking when the braking operation is performed during traveling by the vehicle
at medium to high vehicle speed.
[0098] As fuel cutting conditions for performing this fuel cut control, the following conditions
(a) to (e) are provided as AND conditions.
- (a) Forward range is selected.
- (b) Vehicle speed Vsp is the set vehicle speed Vsp2 or greater (medium to high vehicle
speed).
- (c) The accelerator is off.
- (d) The brake is on.
- (e) The engine speed Ne is a set recovery rotation speed Ner or greater.
[0099] The big differences are that in contrast to having the brake off as one of the conditions
with the sailing stop conditions, with the fuel cutting conditions, having the brake
on is one condition, and the engine speed condition is added with fuel cutting conditions.
[0100] Having the fuel cutting conditions be set to having the brake on is because the purpose
is to strengthen engine braking with this fuel cut control.
[0101] Also, having the engine speed condition added to the fuel cutting conditions is to
avoid the occurrence of stalling of the engine 1 (engine stall) during fuel recovery
(restarting fuel injection) from fuel cutting.
[0102] With the third control unit 61, based on detections signals from each of the sensors,
the fuel cutting conditions of the abovementioned conditions (a) to (e) are determined,
and when the fuel cutting conditions are established, fuel cut control is implemented,
and when the fuel cutting conditions become not established during fuel cut control,
the fuel cut control is ended.
[0103] With this fuel cut control, with the transmission 100 in a power transmitting state
and with a decrease in the power transmitting loss, fuel supply to the engine 1 is
stopped, and the shift ratio of the variator 3 is downshifted to the low side.
[0104] To put the transmission 100 in a power transmitting state, it is sufficient for the
forward clutch 41 to be engaged, and to decrease the power transmitting loss of the
transmission 100, the lock-up clutch 20 can be completely engaged (engagement).
[0105] In this way, when the lock-up clutch 20 is completely engaged, there is the risk
of engine stall occurring if the engine speed Ne is not high to a certain degree at
the time of fuel recovery, and because of that, the engine speed condition (e) was
added to the fuel cutting conditions.
[0106] This fuel cut control may be started after going through return control from sailing
stop control by operating the brake from off to on during sailing stop control.
3. Operation and Effects
[0107] The vehicle control device of an embodiment of the present invention has the configuration
described above, so vehicle control is implemented as shown in the flow chart of FIG.
4, for example. With the flow chart in FIG. 4, the vehicle starts by its key being
switched on, a prescribed control cycle is repeatedly implemented, and it ends by
the key being switched off.
[0108] As shown in FIG. 4, first, a determination is made of whether in sailing stop control
or not (step S10), and if in sailing stop control, a determination is made of whether
sailing stop cancellation conditions are established (step S20), and if not in sailing
stop control, a determination is made of whether sailing stop conditions are established
(step S40).
[0109] For determination of the sailing stop cancellation condition by step S20, a determination
is made for the abovementioned conditions (A) to (D), and if any of conditions (A)
to (D) is not established, it is determined that the sailing stop cancellation condition
is established.
[0110] For the determination of sailing stop conditions by step S40, a determination is
made regarding the abovementioned conditions (A) to (D), and if all of conditions
(A) to (D) are established, it is determined that the sailing stop conditions are
established.
[0111] When not during sailing stop control, and when it is determined using step S40 that
the sailing stop conditions are not established, normal control (step S60) is implemented.
[0112] With this normal control, while maintaining the engaged state of the forward clutch
41, the output of the engine 1 is controlled according to the accelerator opening
degree APO, and the shift ratio of the variator 3 is controlled according to a preset
shift map.
[0113] Also, during normal control, during travel of the vehicle at medium to high vehicle
speed, when a braking operation is performed and fuel cutting conditions are established,
fuel cut control is performed that stops the fuel supply to engine 1, suppressing
the fuel consumption amount, and also strengthening engine braking.
[0114] On the other hand, when in sailing stop control, when it is determined by step S20
that the sailing stop cancellation condition is established, and when not in sailing
stop control, when it is determined by step S40 that sailing stop conditions are established,
sailing stop control (step S50) is implemented.
[0115] With this sailing stop control, implemented are: control to turn off (release) the
forward clutch 41 and put the transmission 100 in the neutral state (step S502), control
to stop the engine 1 (step S504), control to fix the shift ratio to highest level
(step S506), and control to turn off (release) the lock-up clutch 20 (step S508).
[0116] On the other hand, during sailing stop control, when it is determined by step S20
that the sailing stop cancellation condition is established, return control (step
S30) is implemented that cancels the sailing stop control and returns to normal traveling.
[0117] With this return control, starting of the engine I and engaging of the forward clutch
41 arc implemented, but prioritization of engagement of the forward clutch 41 and
downshifting of the variator 3 is implemented based on the vehicle deceleration level
d by the braking operation.
[0118] In other words, starting of the return control and also start control of the engine
1 are performed (step S302), a determination is made of whether the sailing stop cancellation
condition is established by the brake being on (step S304), and if the sailing stop
cancellation condition is established by the brake being on, a determination is made
of whether the vehicle deceleration level d is the determination threshold value d
V or greater for each vehicle speed (step S306).
[0119] When the sailing stop cancellation condition being established is not by the brake
being on, or when the sailing stop cancellation condition being established is due
to the brake being on, but the vehicle deceleration level d is less than the threshold
value d
V, return control back to normal is performed.
[0120] This return control to normal gives priority to engagement of the forward clutch
41, so first, engagement control of the forward clutch 41 (step S316) is performed,
and then a determination is made of whether engagement of the forward clutch 41 is
completed (step S318).
[0121] Engagement control of the forward clutch 41 (step S316) is performed until it is
determined at step S318 that engagement of the forward clutch 41 is completed. The
processes of step S316 and step S318 are performed at prescribed control cycles until
it is determined that engagement is complete.
[0122] At step S318, when it is determined that engagement is completed, return control
ends, and at the next control cycle, via step S10 and step S40, the normal control
is implemented (step S60).
[0123] When sailing stop cancellation is due to the brake being on, and the brake continues
being on, after returning to normal control, downshift control of the variator 3 is
implemented.
[0124] In contrast to this, when the sailing stop cancellation condition is established
by the brake being on, and the vehicle deceleration level d is the threshold value
d
V or greater, return control is performed with downshifting of the variator 3 having
priority.
[0125] With the return control in this case, first, downshift control of the variator 3
is implemented (step S308), downshifting of the variator 3 progresses, and a determination
is made of whether the shift ratio is at the lowest level (step S310).
[0126] The downshift control of the variator 3 of step S308 is performed until it is determined
at step S310 that the shift ratio has reached the lowest level. The process of step
S308 and step S310 is performed at prescribed control cycles until it is determined
to be the lowest level at step S310.
[0127] When a determination of lowest level is made at step S310, the engagement control
of the forward clutch 41 is performed (step S312), and a determination is made of
whether or not engagement of the forward clutch 41 is completed (step S314). Though
not shown in FIG. 4, even before a determination of lowest level is made, even when
the accelerator pedal is pressed during downshifting of the variator, the process
moves to the clutch engagement process.
[0128] The engagement control of the forward clutch 41 of step S312 is performed until it
is determined at step S314 that engagement of the forward clutch 41 is complete. The
processes of step S312 and step S314 are performed at prescribed control cycles until
it is determined that engagement is complete.
[0129] When it is determined that engagement of the forward clutch 41 is complete, return
control ends, and at the next control cycle, normal control (step S60) is implemented
via step S10 and step S40.
[0130] Next, referring to the time charts of FIG. 5 to FIG. 7, various examples of return
control with this control device are explained. In FIG. 5 to FIG. 7, SS indicates
the sailing stop control state, SS return indicates the return control state, stop
indicates the vehicle stop state, and FC indicates the fuel cut control state.
[0131] FIG. 5 shows each variation example of the vehicle speed, brake, each rotation speed,
and shift ratio when the sailing stop control cancellation condition is established
by the brake being on, and when the vehicle deceleration level d when this condition
is established is threshold value d
V or greater. (a) shows a case when this control is applied, and (b) shows a case when
this control is not applied.
[0132] As shown in FIG. 5 (a), when the braking operation is done at time t
11 during sailing stop control, the brake is switched from off to on, the sailing stop
control cancellation condition is established, and the control for returning from
sailing stop control to normal control is started.
[0133] Here, the vehicle deceleration level d when the cancellation condition is established
is the threshold value dv or greater, and to perform return control with downshifting
of the variator 3 prioritized, the engine 1 start operation is performed immediately
after the start of return control, and also the operation of downshifting the target
shift ratio Rt to the lowest side is started.
[0134] Together with starting of the engine 1, the engine speed Ne rises, and together with
that, the primary shaft rotation speed Np of the variator 3 and the secondary shaft
rotation speed Ns of the variator 3 rise.
[0135] At this time, since the lock-up clutch 20 of the torque converter 2 is released,
the primary shaft rotation speed Np is raised so as to follow the engine speed Ne,
and the secondary shaft rotation speed Ns is raised so as to be proportional with
the primary shaft rotation speed Np with the shift ratio at the start of return control
(lowest level or approximately lowest level).
[0136] Thereafter, at the time t
12 at which the engine 1 start is completed, changing to the downshift side of the target
shift ratio Rt is started, and the target shift ratio Rt gradually changes toward
the lowest level shift ratio.
[0137] The actual shift ratio R is also changed to the downshift side from time t
13 following the target shift ratio Rt, and the secondary shaft rotation speed Ns decreases
relative to the primary shaft rotation speed Np.
[0138] After starting of the engine 1, until the discharge pressure of the oil pump 10P
reaches a state that can be used for control, it is not possible to implement downshifting
of the actual shift ratio R, so time lag occurs between the downshift start time t
12 of the target shift ratio Rt and the downshift start time t
13 of the actual shift ratio R.
[0139] Thereafter, the vehicle stops at time t
14, and immediately after this vehicle stop, the actual shift ratio R is downshifted
to the lowest level, and after that, a command is given to engage the forward clutch
41 at time t
15.
[0140] Even when the vehicle is stopped, the forward clutch 41 is in a released state and
the variator 3 is able to rotate, so if the engine 1 is operating, it is possible
to ensure the discharge pressure of the oil pump 10P, and possible to engage the forward
clutch 41.
[0141] By doing this, engagement of the forward clutch 41 is completed at time t
16, rotation of each of the variator 3 primary shaft, secondary shaft, and transmission
output shaft is stopped, and the variator 3 primary shaft rotation speed Np, the variator
3 secondary shaft rotation speed Ns, and the transmission output shaft rotation speed
No are all 0.
[0142] Therefore, the vehicle stops in a state for which the shift ratio of the variator
3 is at its lowest level. For this reason, it is possible to perform restart of the
vehicle in a state with the shift ratio at the lowest level, and possible to ensure
good starting performance of the vehicle.
[0143] In contrast to this, with the return control performed in the same kind of state
as the case shown in FIG. 5 (a), a command is given to start the engine 1, and when
a command is given simultaneously to engage the forward clutch 41 and to downshift
the variator 3, the result is as shown in FIG. 5 (b).
[0144] In other words, as shown in FIG. 5 (b), at time t
11 during sailing stop control, the braking operation is done (brake goes from off to
on), the sailing stop control cancellation condition is established, and return control
is started.
[0145] The start operation of the engine 1 is performed immediately after return control
start time t
11, and furthermore at time t
12 at which the engine 1 start completion is determined, an instruction is given to
engage the forward clutch 41 and to change the target shift ratio Rt to the downshift
side.
[0146] The engagement responsiveness of the forward clutch 41 is higher than the downshift
responsiveness of the variator 3, so the engagement of the forward clutch 41 is completed
at time t
13' which is earlier than the completion of downshifting, and the variator 3 secondary
shaft rotation speed Ns matches the transmission output shaft rotation speed No.
[0147] Also, thereafter, downshifting of the variator 3 advances, but at that point in time,
in accordance with a sudden deceleration of the vehicle speed, the variator 3 primary
shaft rotation speed Np and also the secondary shaft rotation speed Ns decelerate
at a very low speed, so it is difficult for downshifting of the variator 3 to advance,
and at time t
14' before downshifting of the variator 3 advances, the vehicle stops in a state with
the forward clutch 41 engaged, and the variator 3 also stops.
[0148] Therefore, in a state with the downshifting of the variator 3 not advancing, specifically,
in a state for which the shift ratio of the variator 3 is not at the lowest level
or approaching near the lowest level, the vehicle stops. For this reason, it is necessary
to perform restart of the vehicle in a state with the shift ratio at the high side,
and there is a decrease in the start performance of the vehicle.
[0149] FIG. 6 shows examples of each change of the vehicle speed, brake, each rotation speed,
and shift ratio when at time t
21, the sailing stop control cancellation condition is established by the brake being
on, and the deceleration level d of the vehicle when this condition is established
is less than the threshold value d
V.
[0150] In this case, to perform return control with engagement of the forward clutch 41
having priority, the engine 1 start operation is performed immediately after the return
control start time t
21, and furthermore, at time t
22 after the engine 1 start completion determination, the operation of engaging the
forward clutch 41 starts.
[0151] Also, from time t
23 at which engagement of the forward clutch 41 is completed, the target shift ratio
Rt is downshifted to the lowest side.
[0152] In this case, even at the time t
23 when the engagement of the forward clutch 41 is completed, the vehicle speed Vsp
is high to a certain degree, and there is some time to spare until the vehicle stops
thereafter, so downshifting of the variator 3 is completed before the vehicle stops.
[0153] Also, the engagement of the forward clutch 41 is performed in a state with the variator
3 shift ratio at the high side, so it is possible to quickly complete rotation synchronization
between input and output before engagement of the forward clutch 41, and possible
to quickly engage the forward clutch 41.
[0154] In this way, when it is possible to quickly engage the forward clutch 41, when the
brake continues to be on even after that, it is possible to complete control in a
short time, even including the time until downshifting of the variator 3 shift ratio
to the lowest level.
[0155] Of course, before the vehicle stops, downshifting of the variator 3 shift ratio to
the lowest level is completed, so it is possible to ensure good start performance
when doing restart thereafter.
[0156] FIG. 7 shows examples of each variation of the vehicle speed, brake, each rotation
speed, and shift ratio when the sailing stop control cancellation condition is established
at time t
31 by the brake being on, and the vehicle deceleration level d when this condition is
established is less than the threshold value d
V, and when the vehicle speed is higher or the vehicle deceleration level d is smaller
than the case in FIG. 6.
[0157] In this case, to perform return control with priority for engagement of the forward
clutch 41, the engine 1 start operation is performed immediately after return control
start time t
31, and also, the engagement operation of the forward clutch 41 starts at time t
32 after it is determined that the engine 1 start is complete.
[0158] Also, from time t
33 at which engagement of the forward clutch 41 is completed, the target shift ratio
Rt is downshifted to the lowest level side.
[0159] In this case as well, even at time t
33 when engagement of the forward clutch 41 is completed, the vehicle speed Vsp is high
to a certain degree, and there is some spa time until the vehicle stops after that,
so downshifting of the variator 3 is completed before the vehicle stops.
[0160] Also, engagement of the forward clutch 41 is performed with the variator 3 shift
ratio in a high side state, so it is possible to quickly complete the rotation synchronization
between input and output before engagement of the forward clutch 41, and it is possible
to engage the forward clutch 41 quickly.
[0161] In this way, when it is possible to engage the forward clutch 41 quickly, it is possible
to complete the return control in a short time including the time until downshifting
of the variator 3 shift ratio thereafter to the lowest level is completed.
[0162] In this case, at time t
33 when engagement of the forward clutch 41 is completed, the vehicle speed Vsp is sufficiently
high, the "vehicle speed Vsp is the set vehicle speed Vsp2 or greater" of condition
(b) of the fuel cutting conditions is satisfied, all of fuel cutting conditions (a)
to (e) are established, and fuel cut control is implemented.
[0163] With this fuel cut control, in a state with the forward clutch 41 engaged and a state
with the variator 3 shift ratio near the lowest level, the supply of fuel to the engine
1 is stopped, and engagement of the lock-up clutch 20 is strengthened (engagement
at time t
34). By doing this, the fuel supply to the engine 1 is stopped, the fuel consumption
amount is suppressed, and it is possible to strengthen engine braking.
[0164] Also, by engaging the forward clutch 41 having priority, it is possible to complete
control in a short time, including the time until downshifting of the variator 3 shift
ratio to the lowest level is completed, so it is possible to increase the opportunities
for this kind of fuel cut control, and possible to promote suppression of the fuel
consumption amount.
5. Other
[0165] Above, an embodiment of the present invention was explained, but the present invention
is not limited to those embodiments, and it is also possible to carry out the invention
using a portion of this embodiment or by changing a portion of this embodiment.
[0166] For example, it is also conceivable to further add [Condition (E)] for which the
variator 3 shift ratio is the highest level as an AND condition to the sailing stop
conditions (A) to (D) of the abovementioned embodiment.
[0167] In the state with sailing stop conditions (A) to (D) established, in many cases,
the variator 3 shift ratio is at the highest level, but with the vehicle speed Vsp
in the medium speed range, immediately after the accelerator is switched from on to
off, it is assumed that there are cases when the variator 3 shift ratio is not at
the highest level (however, it will be close to the highest level).
[0168] In this case, when condition (E) is added, when the accelerator is turned off, the
shift ratio moves to the highest level, sailing stop control is implemented waiting
for this, and it is possible to further suppress the decrease in vehicle speed with
the sailing stop control thereafter.
[0169] Also, with the abovementioned embodiment, with implementing control with downshifting
of the variator 3 by the second control unit 62 having priority as a prerequisite,
having the sailing stop cancellation condition established by having the brake on
is added (step S304 in FIG. 4), but normally, unless the brake is on, it is thought
that the vehicle deceleration level d will not become the threshold value d
V or greater, so the determination of the prerequisite can be omitted.
[0170] With the abovementioned embodiments, the engagement element for disconnecting/connecting
the transmission of the driving force of the present invention is the forward clutch
41, but as this engagement element, typically, with the forward engagement element
as the focus, instead of the forward/reverse switching mechanism 4, for example, it
is possible to use a forward engagement element such as an auxiliary transmission
mechanism that is a stepped transmission mechanism with two forward gears and one
reverse gear, or each engagement element of two forward gears, the first forward gear
and the second forward gear.
[0171] Also, with the abovementioned embodiment, the control means was configured with hardware
from each control unit of the travel ECU 6 as the travel control means, the ATCU 7
as the shift control means, and the engine ECU 8 as the engine control means, but
the hardware configuration for these travel control means, shift control means, and
engine control means is not limited to this, and for example, it is possible to use
various configurations such as providing each function of the travel control means,
shift control means, and engine control means inside one control unit, etc.